The JSA was under the direction of J. Edgar Hoover and often fought against Adolph Hitler's nazi forces as well as thwarting attempts to assassinate President Franklin Delano Roosevelt. They served their country and the Allies well. Those members of the JSA fought alongside one another while simultaneously having separate adventures and attending to the personal lives of their alter-egos. As the war came to an end, the JSA remained active with an irregularly rotating roster of new and old heroes serving under its banner. They turned their attentions to organized crime rings, strange alien energy creatures that threatened invasion, and many costumed villians including the Brain Wave, Solomon Grundy, and the Injustice Society of the World.

In the years since 1985 after DC's Crisis on Infinite Earths, many liberties have been taken with the history of the JSA. One major point is that Superman, Batman and many of the heroes which are still making them a lot of money in modernized versions today never actually existed. There's only allegedly one Earth now. So since in the new continuity those characters didn't exist in 1939 when in fact they did, the stories from those old days involving certain characters are no longer considered canon. It's really rather silly when you stop to think about it.